Stretch forming is a metal bending process in which a lineal shape (as an aluminum extrusion) is stretched and bent simultaneously over a form, called a die, which has been built to the radius needed. Stretch forming is performed on a stretch form press, in which the lineal shape is securely gripped on each end by gripping jaws. The stretch form gripping jaws are each attached to a carriage that is pulled by hydraulic force to stretch and curve the metal. The tooling used in the stretch forming process is a stretch form block, called a stretch form die, which is a solid contoured piece against which the lineal shape will be formed to a curve. Stretch formed parts can be up to 16” in circle size depending on the stretch form press being used. Stretch forming allows for high accuracy and smooth surfaces. Tight radii can be attained through stretch forming that cannot be attained with other curving methods. Ductile materials are preferable in stretch forming, the most commonly used being aluminum and steel. Stretch formed parts are commonly seen on arches in commercial buildings. Other stretch formed parts can be found in curved window frames, conveyors, signs, displays, etc. There are many applications for curved metal where stretch forming is the only feasible method for curving.
Southern Stretch Forming: “We don’t bend metal. We curve metal.”